LARES Lexicon Acoustic Reverberance Enhancement System

exicon How LARES can Help Meet the Objectives of Good Acoustical Design". Sound Reinforcement Reinforcing Early Reflections In this application LARES principles yield an in­ The perceived loudness of a sound in a hall depends crease in gain-before-feedback of 6 -18 dB. The both on the loudness of the direct sound and on the amount of improvement depends on the number of amount of early reflected energy which adds to the microphones, loudspeaker channels, and number direct sound. The level of the first few strong of Lexicon's Advanced DSP processors. For ex­ reflections is determined primarily by the hall ge­ ample, the increase is 15 dB with two microphones, ometry. Careful placement of reflecting surfaces in four loudspeaker channels, and one Lexicon 480L the stage, ceiling and side walls can increase this Advanced DSP. With two processors and eight level somewhat by directing sound energy to the loudspeaker channels, the improvement is 18 dB. audience. However, the energy directed to the audience by walls or reflectors is generally ab­ With such a large increase in gain before feedback sorbed, and is not available to create additional level far fewer microphones need to be employed to or later reverberation. For this and many other reinforce any performance, and the reinforcement is reasons, the total amount of reflected energy de­ hard to distinguish from the natural response of the pends primarily on the amount of absorption in the hall. This type of reinforcement is ideal for boosting hall, which in most halls is proportional to the seating a weak vocalist or chorus in a show, improving stage area. The more people you put in a hall the softer the acoustics through added reflected energy, or add­ sound will be. ing lateral reflections to a hall. In reinforcement applications the LARES software is adjusted to This conflict between hall loudness and seating area provide maximum intelligibility and minimum rever­ is fundamental. It means that small halls will always beration. LARES software also incorporates time sound louder than larger ones, and when a small delays that can be adjusted to insure that the rein­ orchestra plays in a large hall, the sound will not forced sound matches the direct sound. have the the impact and richness that enough level can create.

Acoustic Enhancement LARES can help enormously with this classic acous­ tic dilemma. Since the loudspeakers add energy Spaces that can benefit from LARES may vary in (from the power company) loudness can be in­ size, absorptivity and use. By distinguishing some creased without the penalty to later reverberation. of the desirable properties of rooms used for listen­ To significantly increase the actual acoustic level a ing to music and identifying typical problems en­ large amount of acoustic power will be required - at countered in acoustic spaces, we can see how least as much as the orchestra itself! If a conven­ LARES can be integrated to improve the acoustic tional sound reinforcement system were used to design. provide the power, normal microphone spacings of LARES Matches the Space to the Performance", Reverberance Desired for Various Types of Performance

111111 ••••••••••• Symphony (Romantic Works) 1111111;1111 I III Secu Iar Chor aI Works 11111111,1111~_.i 1111111 Contempor ar y Or chestral WorkS, Recital and Chamber Mus ic 1111111 111 '11111 Ope r a I 1111 11111 Semiclassical Concer ts and Choral Groups Us ing Sound System I 11111111 : : ~ 11111111) I I I Tour ing Br oadway Musical Comed ies, Operettas, Gilbert & Sullivan I .11111111 111,1111111 Dance Bands Etc. Us ing Sound System '11111111 III

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 ReverberationTime in Seconds Reverb Times Typical for Various Performance Spaces I I I I I I Small Churches Large Churches Cathedrals 1111111 i Concert Halls .I. 111)1111111 11111111111 Gen era l Pu rpose Au di tori ums 11111111111 11111111 I I Hi gh Sc hoo l Au ditor iums 1111111111 III 1111 Smal I Theatres 1111fIIlII~ 1111 Cinema I 11I11II._allll Lecture and Conference Rooms 1111 III El ementary Classr ooms I III 1111 I Rec ording and broadcast studies for spe ech only

II rl.,-II .1 I I I I 1 I 1 I I I I I I I I I I 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 ReverberationTime in Seconds As shown in the charts above, spaces often do not provide reverberation that is well suited lor different types 01 performance. LARES can help spaces achieve reverberant characteristics appropriate for both specific and multipurpose use. one meter or less would be required to achieve designed which project reflected energy primarily to adequate level while maintaining low coloration. In the walls instead of directly down on the audience, this application, LARES adds both the reinforce­ and the walls of fan shaped halls can be staggered ment necessary to achieve adequate acoustical so sound reflects primarily back across the audito­ power and provides reverberant enhancement. With rium. LARES, a much greater microphone distance can be used eliminating the need for operator interven­ Such features may increase the lateral fraction, but tion or a carefully mixed close microphone array. may not increase the total lateral energy. The And unlike a conventional reinforcement system, features are probably a good idea, but even with the energy added from LARES will not be audibly them LARES can help considerably. In our experi­ artificial. ence and that of J . Bradley at the NRC in Canada, spaciousness depends primarily on the absolute Where the initial time delay gap in an existing hall is strength of the lateral energy, not necessarily in the too large the LARES software and an array of early lateral fraction. LARES systems are particu­ speakers (hidden in the ceiling or disguised as larly effective in raising the lateral energy, and can lighting or sculpture) can fill in the missing energy, be designed to increase the early lateral fraction if and do it without any artificial tone color. Such a this is desired. LARES array can also supply the missing lateral energy in fan shaped designs without any alteration We have found that a uniform ceiling array of high to the desirable sight lines such shapes provide. quality non-directional speakers combined with our multi-channel digital electronics can successfully In larger spaces, the control of reverberation time create a diffuse sound field with high lateral energy. and level that LARES provides makes it possible to In the Elgin Theater (Toronto, Ontario, Canada) 56 design a large hall with short audience seating speakers under the balcony combined with special distances and good sight lines while maintaining LARES software and hardware produce a sound world class reverberance. Such a hall could be field which seems to come from all around the optimized for both symphony and opera, with their listeners, even if they stand only 5 feet below one of very different acoustical requirements. The LARES the speakers. There are no echoes even on percus­ equipped hall would have the advantage of adjust­ sive material, and the sound field does not reduce able acoustics without the expense of motorized the intelligibility of speech. The lateral energy in­ drapes or mechanical doors opening to reverbera­ creases at least 4 dB when this array is activated, tion chambers. Since changes to the reverberation and the increase in spaciousness is impressive. are silent and fast, it is easy to optimize the hall for The ceiling seems to disappear, to be replaced by a a particular piece in real time. With the A. R. C. very convincing illusion of the hall above. (Automatic Reverberance Control) circuit provided in LARES, it is also possible to achieve a much Improved Control Over Late higher richness and spaciousness in opera produc­ tions without compromising dialog. Reverberation Level Enhanced Spaciousness Our experience with recorded music has lead us to believe that the ratio of direct sound to reverberant sound is quite critical. Too little reverberant level The vital acoustic property of spaciousness or spa­ and music sounds flat and lifeless. Too much makes tial impression depends on having adequate reflec­ the sound garbled and muddy. The same appears tions that come from the sides of the listener. With­ to be true of halls. In classical acoustics this ratio out electro-acoustics, the direction of reverberation depends primarily on the geometry of the hall and energy depends primarily on the shape of the hall. where you sit, but in the best halls the reverberant Halls of rectangular or inverse fan shape have a sound is never inaudible, and the music is never higher fraction of early lateral reflections than square obscured. or fan shaped halls. Once the importance of lateral energy was recognized by acousticians many clever ways increasing it were invented and incorporated into hall designs. For example, ceilings can be • The reverberant level also depends on the size of In a small hall the problem is reversed. Conven­ the hall. In a small hall there may not be adequate tional wisdom for designing such a space would try audience seating area to absorb the sound. The to make every surface that did not hold the audience reverberant level can be high, and the reverberation as reflective as possible in an effort to increase the time can be too short. If the hall designers wish to reverberation time. However, unless the audience achieve a reverb time of 1.5 to 2 seconds in spite of is willing to sit on wooden benches with very little • the small volume they will probably attempt to re­ clothing such effort will not increase the reverbera­ duce the absorption of everything as much as pos­ tion time very much. If we succeed in raising the sible, further increasing the reverberant level. This reverberation time by this means we will also in­ • acoustical treatment will make the hall too loud and crease the reverberant level and the resulting sound too muddy, particularly for an audience accustomed may well be muddy, loud, and unintelligible. to recorded music. LARES can help both large and small halls enormously. In larger spaces it can provide long If LARES were incorporated into the design of this reverberant decay without requiring high ceilings. small hall, absorption would be added to reduce the The sound will be louder and better. In small spaces natural reverberation to tolerable levels. This may it allows rooms to be constructed with more ordinary well be easier than it sounds in a new design, since materials and acoustically treated with absorption to ·- there is no need to make all the surfaces as reflect­ . minimize initial reflections and slap echoes. Once ing as possible. LARES will supply the needed the natural reverberant level has been reduced reverberation at a level and a reverberation time enough to give good articulation LARES can provide appropriate to the music. The architect should work the needed reverberant decay. The decay time and to keep enough absorption in the structure to mini­ the reverberant level can be manually or automati­ mize "muddyness", and to prevent large acoustic cally adjusted with the LARES A. R. C. (Automatic differences when the hall is occupied and unoccu­ Reverberance Control) circuit to match the needs of pied. LARES can minimize the difference in rever­ music or speech. berant character due to changing audience num­ bers in such a space, providing more consistent LARES and Stage Enclosures performances and better listening enjoyment. By reducing the level of the loudspeakers furthest away from the sound sources LARES can also be ad­ The problem of providing musicians with the opti­ justed so that more of the seats can experience mum environment for playing is closely related to optimum reverberation level. the problem of sound reinforcement. Normally it is assumed that when musicians cannot hear each other it is because there are too few stage reflec­ Enhanced Late tions. LARES can directly help this problem. Reverberation Time However, we have found that particularly when the stage is small the reflected sound of the musicians' Another inescapable fact of natural acoustics is that own instruments masks the sound from the rest of the total absorption usually depends almost entirely the orchestra. In this case the solution is to add • on the total seating area, and the reverberation time absorption to the stage surfaces, and replace the of a hall depends on the volume of the hall divided energy lost with a LARES system who's micro­ by the total absorption. If we want to seat a large phones have been carefully balanced to pick up the number of people the absorptive surface area will be whole orchestra. Lexicon in conjunction with BB&N large. If we want to keep the reverberation time has installed a LARES system and about 1000 sqft. constant at 2 seconds as the number of listeners of absorption in a small hall in Concord MA, and the increases we will have to also increase the volume improvement in stage acoustics is enormous. Many of the hall. Hall volume is expensive, both to build of the orchestra members spontaneously informed and to heat. Furthermore, if we raise the ce iling us that it was the first time they had been able to hear overhead reflections will arrive at the audience too the whole orchestra. late. Reflecting panels will have to be hung to reduce the initial time gap. In this application the LARES system must produce About Lexicon a high acoustic level in the direct vicinity of the microphones, and the time delays between the In 1971 Lexicon introduced the world to direct and the LARES energy had to be short. To digital audio. Ever since, Lexicon has re­ achieve short enough delays and adequate gain mained at the forefront of digital audio tech­ before feedback the four microphones had to be nology. The Lexicon 224 Digital Reverbera­ hung over the orchestra, not out in the hall. tion system revolutionized techniques now used daily in the modern recording industry. In Corcord, one Lexicon 480L Advanced DSP proc­ Today, Lexicon produces a wide variety of essor was used to increase optimally timed energy digital audio products for both the profes­ in the stage area. This system provided an "electro­ sional and consumer. acoustic bandshell" that allowed the musicians in the orchestra to hear each other better and many felt Recent advances in digital signal process­ that it improved the performance. Another Lexicon ing, combined with Lexicon's extensive re­ 480L Advanced DSP processor receiving signal search in natural acoustics and digital rever­ from the same microphones was used to provide the beration algorithms, have produced the long reverberation time needed in the hall. The A. R. LARES system and LARES software. This C. (Automatic Reverberance Control) circuit auto­ development represents a breakthrough in matically tailored the longer reverberation level as the way both electro-acoustics and classical different pieces of music were performed. acoustics are utilized to enhance the versa­ tility and perceived quality of both the venue Applying the Appropriate and the performance. Technology

In many spaces excellent acoustics can only be achieved through a combination of electro-acous­ tics and careful application of conventional sound absorption and diffusing surfaces. For this reason Lexicon works directly with acousticians, architects, and sound installers on-site to determine the most appropriate treatment for the given space. We have developed the measurement tools and experience to evaluate the current acoustics and to find the optimum solution. In general, if a room is to be used for both speech and music any problem with unam­ plified speech intelligibility should be identified and corrected before an electro-acoustic enhancement system is completed. LARES -- A Dynamic New Tool for Improving Room Acoustics". The Lexicon Acoustic Reverberance Enhancement It incorporates sophisticated digital signal process­ System (LARES) is a method of augmenting the ing techniques that overcome the noticeably artifi­ natural direct and reflected energy in halls, perform­ cial sound of electro-acoustic systems when signifi­ ance spaces, places of worship, and spaces that cant acoustic feedback is present. requ ire flexible acoustical character. LARES uses microphones, advanced digital electronics, and loudspeakers to generate energy at the optimal LARES Software -- designed to time, loudness, and reverberant decay that greatly be experienced, not heard enhances the pleasure of listening within an envi­ ronment. The enormous increase in gain before The unique software used in LARES provides both feedback, and decrease in coloration that LARES feedback reduction and/or high quality reverbera­ provides over conventional sound systems consti­ tion. When employed in electro-acoustical applica­ tutes a breakthrough in acoustical enhancement tions LARES software is far superior to algorithms and sound reinforcement. designed for use in the recording industry, providing both a remarkable improvement in gain before feed­ The LARES system can: back (at least 12 dB) and reduced tone coloration. A properly installed LARES system also makes the • Increase the gain before feedback of a conven­ added energy difficult to localize, which allows the tional distributed sound reinforcement system. acoustician unprecedented freedom when choos­ The increase in gain that LARES can supply ing microphone and loudspeaker positions. depends on the number of processors and loud­ speaker channels employed, but is typically 12 to LARES can reduce or eliminate many of the difficult 18 dB. problems of classical acoustics, particularly prob­ lems where the existing reflected energy is too weak • Increase the reverberant level as well as the or arrives at the listeners too late. The simple control reverberation time in halls and churches of all offered by LARES also allows a multi-use space to sizes. The resulting electro-acoustic reverbera­ be much more successfully shared between groups tion enhancement is both musically convincing that require very different acoustics, such as dram.a and wholly natural sounding. In the current and symphony. Unlike fixed architectural acoustic installations, reverberant level (G) has been treatments, LARES can be altered in real time with enhanced by 3 dB or more using only two micro­ no artifacts. Another unique feature of the LARES phones hidden up to 50 feet away. software is the A. R. C. (Automatic Reverberance Control) circuit that can distinguish between musi~ • Increase the reverberant time without increasing and speech and adjust reverberant level automati­ the reverberant level in spaces that are already cally. With A. R. C , the LARES system maintains too live and muddy. optimum spaciousness and intelligibility. for the performance in real time without operator interven­ • Improve the stage acoustics in performance tion. spaces, allowing musicians to hear each other clearly and at the appropriate musical level. Flexible Acoustic Control Distinctly Natural Performance The LARES system also provides Lexicon Dynamic MIDI ® control that can be linked with many current The LARES system is the result of ongoing research lighting and sequencing systems creating possibili­ and development in the field of reverberant simula­ ties for ambience alteration that until now did not tion that stems from Lexicon's 20 years of experi­ exist. ence in building professional digital audio products. At the heart of the system is Lexicon's Advanced DSP hardware (the Lexicon 480L) and LARES software. LARES software has been specifically developed for acoustic enhancement and reinforce­ ment.